2 files changed, 17 insertions, 4 deletions
diff --git a/src/script/api/qscriptengine.cpp b/src/script/api/qscriptengine.cpp
index 13b8e7c..2417d80 100644
--- a/src/script/api/qscriptengine.cpp
+++ b/src/script/api/qscriptengine.cpp
@@ -1067,11 +1067,15 @@ void QScriptEnginePrivate::setGlobalObject(JSC::JSObject *object)
     if (object == globalObject())
         return;
     QScript::GlobalObject *glob = static_cast<QScript::GlobalObject*>(originalGlobalObject());
-    if (object == originalGlobalObjectProxy)
+    if (object == originalGlobalObjectProxy) {
         glob->customGlobalObject = 0;
-    else {
+        // Sync the internal prototype, since JSObject::prototype() is not virtual.
+        glob->setPrototype(originalGlobalObjectProxy->prototype());
+    } else {
         Q_ASSERT(object != originalGlobalObject());
         glob->customGlobalObject = object;
+        // Sync the internal prototype, since JSObject::prototype() is not virtual.
+        glob->setPrototype(object->prototype());
     }
 }
 
diff --git a/src/script/api/qscriptvalue.cpp b/src/script/api/qscriptvalue.cpp
index 7469f9a..1310c8c 100644
--- a/src/script/api/qscriptvalue.cpp
+++ b/src/script/api/qscriptvalue.cpp
@@ -538,19 +538,28 @@ void QScriptValue::setPrototype(const QScriptValue &prototype)
                  "a different engine");
         return;
     }
+    JSC::JSObject *thisObject = JSC::asObject(d->jscValue);
     JSC::JSValue other = d->engine->scriptValueToJSCValue(prototype);
 
     // check for cycle
     JSC::JSValue nextPrototypeValue = other;
     while (nextPrototypeValue && nextPrototypeValue.isObject()) {
         JSC::JSObject *nextPrototype = JSC::asObject(nextPrototypeValue);
-        if (nextPrototype == JSC::asObject(d->jscValue)) {
+        if (nextPrototype == thisObject) {
             qWarning("QScriptValue::setPrototype() failed: cyclic prototype value");
             return;
         }
         nextPrototypeValue = nextPrototype->prototype();
     }
-    JSC::asObject(d->jscValue)->setPrototype(other);
+
+    thisObject->setPrototype(other);
+
+    // Sync the internal Global Object prototype if appropriate.
+    if (((thisObject == d->engine->originalGlobalObjectProxy)
+         && !d->engine->customGlobalObject())
+        || (thisObject == d->engine->customGlobalObject())) {
+        d->engine->originalGlobalObject()->setPrototype(other);
+    }
 }
 
 /*!